Computer screens and other two-dimensional (2D) surfaces are commonly used for displaying 2D visual content such as a page of text, a diagram or a Web site page. Some forms of visual content contain two or more content forms, such as a page consisting of text and diagrams, or a Web site page containing information related to the site and unrelated advertising. Usually, only one page is displayed on a screen at a time and the page is confined to the boundaries of the screen. The different elements in a page must therefore compete with each other for space and the viewer's attention, even if they are related to each other Existing Web site pages are therefore generally overcrowded by advertising and this is the major reason why Web advertising is presently considered ineffective.
Changing a displayed page (known as browsing or navigating) is a discontinuous process wherein an initially displayed page is removed from the screen and a second page is subsequently displayed. The ability to view only one page at a time makes it difficult for a viewer to know his location at a website and also creates uncertainty while navigating through the site. Changes in the size of a page is also done in discrete steps, and a return to the browser is required for each step change.
It is also known to arrange several pages in a virtual three-dimensional (3D) space and projecting a portion of the 3D space onto the 2D screen. A viewer may continuously navigate from page to page.
Robertson et al (Data Mountain: using Spatial memory for document Management) disclose a method for document management which allows users to place documents at arbitrary positions on an inclined plane in a 3D desktop virtual environment using a 2D interaction technique. The pages are all viewed en face perpendicular to the user's perspective). Robertson et al (Task Gallery: a 3D Window Manager) disclose a method for task management and document comparison. Application windows appear unaltered as artwork hung on the walls of a virtual art gallery, with a selected task on a back wall. The perspective from which the gallery is viewed is perpendicular to the back wall of the gallery, so that documents hung on the back wall are viewed en face, while documents on the side walls, floor and ceiling are parallel to the user's perspective. Multiple documents can be selected and displayed side-by side using 3D space to provide uniform and scaling.